Aiming at influences of bridge deck unevenness on bridge DAF, DAF values of a concrete girder bridge caused by a certain amount of unevenness samples were calculated with a self-compiled program. The results showed that the bridge’s DAF values caused by unevenness samples with the same grade are also discrete; the existing unevenness energy PSD classification method has a certain limitation during its being used in calculating the bridge’s DAF. Statistical analysis was conducted for the DAF set caused by unevenness samples. The results showed that the DAF set caused by unevenness samples with the same grade and independent phase angle of the same distribution obey the normal distribution; aiming at effects of vehicle string on the bridge’s DAF, a genetic algorithm for calculation of fitness with the delay superposition method was proposed. It was shown that this algorithm can be used to reduce the calculation amount of vehicle-bridge coupled vibration, effectively do the optimization analysis for vehicle spacing in a vehicle string, and obtain the bridge’s largest DAF under action of vehicle string and the corresponding vehicle string arrangement.